Readers and listeners make provisional or partial commitments at multiple levels of representation as linguistic input unfolds over time. The continuousness of comprehension raises methodological and theoretical challenges. The methodological challenge is to monitor comprehension processes as they are occurring. The theoretical challenge is to develop and evaluate explicit mechanistic models that support real-time comprehension. Such models are essential for understanding normal comprehension and its development, developmental disabilities, and comprehension impairments that arise from brain injury. The goal of this project is to develop and test explicit models of how readers and listeners coordinate linguistic and non-linguistic contextual information in constructing interpretations during real-time language comprehension. The proposed research examines the mechanisms underlying real-time language comprehension within a constraint-based framework emphasizing rich lexical representations and the incremental updating of a discourse model. Two lines of research are proposed. The first extends constraint-based models of ambiguity resolution to evaluate whether they can account for processing differences between different classes of verbs without direct appeal to syntactic complexity. These studies use corpus analyses, ratings, fragment completion, computational modeling, and reading time experiments. The second line of research examines how listeners establish, update, and refer to referential domains as an utterance unfolds over time, and how referential domains affect syntactic ambiguity. Reference must be contextualized to a relevant domain of interpretation. Although this domain ultimately includes information introduced linguistically into the discourse, salient objects in the environment, and shared presuppositions between participants in a conversation, little is known about how and when these different sources of constraint are used. The proposed work uses a head-mounted eye-tracking paradigm in which participants follow spoken instructions to move real objects in a workspace or pictures displayed on a monitor. By manipulating the objects in the display and the instructions, it is possible to determine the time course with which semantic and pragmatic constraints are used in circumscribing referential domains.